Each year stroke affects 800,000 patients in the US, costing an estimated $34B in care. For 250,000 of these patients, the cause of their stroke remains unknown in spite of a thorough clinical workup by a trained stroke clinician. Determining the cause of stroke is the first step in preventing another stroke. In the case of Atrial Fibrillation, which often goes undetected, proper treatment can reduce the risk of another stroke by 65-80%. The ISCDx test finds the cause using gene expression and provides stroke clinicians guidance in their evaluation process.